Android Introduction Based on slides made by Mihail L. Sichitiu and Kesav Kaliyaperumal and also from wikipedia

What is Android? Android is a software stack for mobile devices that includes an operating system, middleware and key applications.

Android OS an open-source operating system based on the Linux kernel designed primarily for touchscreen mobile devices such as smartphones and tablet computers 1 billion Android devices have been activated 48 billion apps have been installed

Phones HTC G1, Droid, Tattoo Motorola Droid (X) Sony Ericsson Suno S880 Samsung Galaxy @2011 Mihail L. Sichitiu

Tablets Velocity Micro Cruz Gome FlyTouch Acer beTouch Toshiba Android SmartBook Cisco Android Tablet Dawa D7 @2011 Mihail L. Sichitiu

Others Google Glasses Portable/Car Devices Watches SmartTV

MarketShare Feb’10 May’10 Apr’11 RIM 42.1% 41.7% 29% Apple 25.4% 24.4% 25% Google 9% 13% 33% Microsoft 15.1% 13.2% 7.7% Palm 5.4% 4.8% 2.9% Now (November 2013): 80% @2011 Mihail L. Sichitiu

Android OS Interface Android's user interface is based on direct manipulation: using touch inputs that loosely correspond to real-world actions, like swiping, tapping, pinching and reverse pinching to manipulate on-screen objects.

Android OS Memory management Android is designed to manage memory (RAM) to keep power consumption at a minimum, in contrast to desktop operating systems which generally assume they are connected to unlimited. When an Android app is no longer in use, the system will automatically suspend it in memory – while the app is still technically "open“.

Android OS Memory management Android manages the apps stored in memory automatically: when memory is low, the system will begin killing apps and processes that have been inactive for a while, in reverse order since they were last used (i.e. oldest first). This process is designed to be invisible to the user, such that users do not need to manage memory or the killing of apps themselves.

Android App Priority and Processes Android apps do not have control over their own life cycles Aggressively manages resources to ensure device responsiveness and kills process/apps when needed Active Process – critical priority Visible Process – high priority Started Service Process Background Process – low priority Empty process

Linux Kernel and Storage Management The flash storage on Android devices is split into several partitions, such as /system for the operating system itself, and /data for user data and application installations. In contrast to desktop Linux, Android device owners are not given root access to the operating system and sensitive partitions such as /system are read-only. However, root access can be obtained by exploiting security flaws in Android.

Software Stack Linux kernel Libraries Android run time core libraries Dalvik virtual machine application layer application protocol

Android Architecture

Android S/W Stack - Application Android provides a set of core applications: Email Client SMS Program Calendar Maps Browser Contacts Etc All applications are written using the Java language. @2011 Mihail L. Sichitiu

Android S/W Stack – App Framework Enabling and simplifying the reuse of components Developers have full access to the same framework APIs used by the core applications. Users are allowed to replace components. @2011 Mihail L. Sichitiu

Android S/W Stack – App Framework (Cont) Features Feature Role View System Used to build an application, including lists, grids, text boxes, buttons, and embedded web browser Content Provider Enabling applications to access data from other applications or to share their own data Resource Manager Providing access to non-code resources (localized strings, graphics, and layout files) Notification Manager Enabling all applications to display customer alerts in the status bar Activity Managing the lifecycle of applications and providing a common navigation backstack @2011 Mihail L. Sichitiu

Android S/W Stack - Libraries Including a set of C/C++ libraries used by components of the Android system Exposed to developers through the Android application framework @2011 Mihail L. Sichitiu

Android S/W Stack - Runtime Core Libraries Providing most of the functionality available in the core libraries of the Java language APIs Data Structures Utilities File Access Network Access Graphics Etc @2011 Mihail L. Sichitiu

JVM

Android S/W Stack – Runtime (Cont) Dalvik Virtual Machine Providing environment on which every Android application runs Each Android application runs in its own process, with its own instance of the Dalvik VM. Dalvik has been written such that a device can run multiple VMs efficiently. Register-based virtual machine @2011 Mihail L. Sichitiu

Android S/W Stack – Runtime (Cont) Dalvik Virtual Machine (Cont) Executing the Dalvik Executable (.dex) format .dex format is optimized for minimal memory footprint. Compilation Relying on the Linux Kernel for: Threading Low-level memory management @2011 Mihail L. Sichitiu

Android S/W Stack – Linux Kernel Relying on Linux Kernel 2.6 for core system services Memory and Process Management Network Stack Driver Model Security Providing an abstraction layer between the H/W and the rest of the S/W stack @2011 Mihail L. Sichitiu